Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
  • B42D25/29—Securities; Bank notes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/30—Identification or security features, e.g. for preventing forgery
  • B42D25/328—Diffraction gratings; Holograms
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/0005—Adaptation of holography to specific applications
  • G03H1/0011—Adaptation of holography to specific applications for security or authentication
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H1/024—Hologram nature or properties
  • G03H1/0248—Volume holograms
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/04—Processes or apparatus for producing holograms
  • G03H1/18—Particular processing of hologram record carriers, e.g. for obtaining blazed holograms
  • G03H2001/186—Swelling or shrinking the holographic record or compensation thereof, e.g. for controlling the reconstructed wavelength

Definitions

• the invention relates to an anti-counterfeit security object and a . method for producing such a sub- strate. It also relates to a method for verifying the authenticity of such an object.
• the security feature com ⁇ prises a hologram layer with a volume hologram.
• Security objects of this type may e.g. be bank notes, passports, credit cards, identity cards, packages or tags for valuable goods, data carriers, let ⁇ terheads, etc. Such objects are often equipped with secu- rity features with the purpose to make counterfeiting difficult.
• volume holograms have also been proposed for such applications, see e.g. EP 1 091 267.
• Volume holograms have gratings of a depth that is much larger than the wavelength of visi ⁇ ble light, e.g. a depth of at least 10 ⁇ m, advantageously at least 50 ⁇ m. They can have high diffraction efficien ⁇ cies, generate powerful images and have well-defined dif ⁇ fraction angles and wavelengths .
• the method for manufacturing an anti-counterfeit security object comprises the steps of creating a volume hologram in a hologram layer, applying the hologram layer to a sub ⁇ strate, and non-homogeneousIy deforming the hologram layer thereby deforming the volume hologram.
• the invention relates to an anti-counterfeit security object comprising a sub ⁇ strate, and a hologram layer with a volume hologram, wherein said hologram layer is arranged on a surface of said substrate, wherein said volume hologram comprises inhomogeneous deformations caused by deformations of said hologram layer.
• the invention relates to a method for verifying the authenticity of the security ob ⁇ ject of the second aspect, said method comprising the steps of illuminating said volume hologram for gener ⁇ ating a reflected light field, checking for the presence of at least one property of said reflected light field caused by said in- homogeneous deformations, and negating the authenticity in the absence of said property.
• a "non-homogeneous" deforma ⁇ tion is a deformation that does not affect the whole hologram in the same manner.
• the hologram is deformed locally, i.e. only in certain areas of the hologram.
• the deformation of the hologram leads to a change in the length and/or direction of the local grat ⁇ ing vector of the volume hologram, which in turn affects the conditions (wavelength and angle) under which light is scattered.
• the deformation can be easily recog ⁇ nized by optical inspection of the hologram. Since the wavelength and angle selectivity in volume holograms is much higher than in surface holograms, deformations be ⁇ come much more apparent in the former.
• the steps of applying the hologram layer to the substrate and of deforming the same can be carried out simultaneously or subsequently.
• the hologram layer is applied over a surface structure of the sub- strate, said surface structure comprising edges of a height of at least 10 ⁇ m, advantageously at least 30 ⁇ m, and leading to a deformation of the hologram.
• An "edge” in this sense is understood to be any variation in height with a slope angle of at least 10°, in particular at least 30° .
• the hologram layer can be deformed by embossing it, either at room temperature or at elevated temperature.
• embossing designates any non-homogeneous de ⁇ formation by applying a non-homogeneous pressure by means of a hard, object, which object is removed after deform ⁇ ing the hologram layer.
• the deformations are applied to areas of the volume hologram where the same is, without deformation, visually substantially homogeneous, e.g. in areas where the length and direction of its local grating vector varies only slowly prior to deformation and much faster after defor- mation. In that case, the deformations can be recognized easily.
• the invention can be applied to any type of security objects.
• the se ⁇ curity object is a bank note, but it can also be a pass ⁇ port, credit card, brand label or any of the security ob- jects mentioned above.
• Fig. 1 is a top view of a bank note with a hologram layer attached thereto,
• Fig. 2 is a schematic sectional view through a hologram layer and part of the substrate with a surface structure
• Fig. 3 is a sectional view of the hologram layer of Fig. 2 prior to deformation
• Fig. 4 is a sectional view of the substrate with its surface structure prior to application of the hologram layer
• Fig. 5 is a sectional view through an em ⁇ bossed hologram layer and part of the substrate, the fig ⁇ ure also schematically depicting the embossing stamp, and Fig. 6 is an example of a hologram comprising a first pattern formed by the undeformed hologram and a second pattern formed by the deformations.
• FIG. 1 shows, as one embodiment of the secu ⁇ rity object according to the present invention, a bank note 1 having conventional imprinted or otherwise applied security features 2, images 3 and value information 4.
• bank note 1 carries one or more hologram layers 5.
• Fig. 2 shows a sectional view through holo ⁇ gram layer 5 and the underlying bank note substrate Ia.
• a surface structure 6 comprising two "bumps" is arranged on top of substrate Ia.
• Hologram layer 5 is non-homogeneousIy deformed to match with the two bumps .
• a volume hologram 7 as shown in Fig. 3 is prepared in hologram layer 5, separate from bank note 1.
• hologram layer 5 is a trans ⁇ parent, thermoplastic foil of homogeneous thickness com ⁇ prising photosensitive material.
• Volume hologram 7 is written into hologram layer 5 by means of e.g. two coher ⁇ ent light beams impinging from opposite sides onto holo ⁇ gram layer 5. After exposure, the hologram is stabilized for making it light resistant. Suitable materials and methods are known to the person skilled in the art and are e.g. described in WO 03/036389 by Xetos AG, Germany.
• Such a surface structure (or at least a part thereof) can e.g. be formed by embossing substrate Ia.
• material for form ⁇ ing the structure can be applied locally to the flat sur ⁇ face of substrate Ia, e.g. by applying the material using intaglio printing. Any other technique, such as other printing techniques, allowing to apply a readily deform- able material to substrate Ia in the form of a structure and then hardening it can be used as well .
• intaglio print ⁇ ing is used and the bumps of surface structure 6 are formed by dye or a hardenable, transparent material.
• intaglio printing is a technique commonly applied in the production of security documents, and therefore the process for forming surface structure 6 is readily incorporated into security print ⁇ ing lines .
• hologram layer 5 can be applied thereto, e.g. using a glue or hot melt techniques.
• hologram layer 5 is heated in order to raise its temperature for softening it when it is in contact with surface structure 6 and substrate Ia, thereby encouraging deformation against surface structure 6.
• pressure can be applied to hologram layer 5 in order to induce deformations.
• the volume hologram in hologram layer 5 can be a phase and/or an absorption hologram. It is oriented such that it scatters at least part of the light 8 im ⁇ pinging on the top surface of hologram layer 5 back as reflected light 9 (see Fig. 2), thus allowing an observer to view the reflected light 9.
• layer 5 is deformed to fit over the bumps of surface structure 6, which leads to local distorted regions 10 in volume hologram 7, where the grating spacing and orientation of volume hologram 7 is different from what it was prior to distortion.
• the direction and wavelength of an incoming light beam 8 must be matched to the local grating spacing and orientation of volume holo ⁇ gram 7. Hence, the reflection conditions change in the distorted regions 10.
• the origi ⁇ nal volume hologram prior to deformation i.e. in the state as shown in Fig. 3, was a homogeneous grating with constant spacing and orientation.
• the light re ⁇ flected from the distorted regions 10 will have different color and intensity than the light reflected from the rest of the hologram.
• the height H of the bumps can be fairly small, typically at least 10 ⁇ m, e.g. in the order of 30 ⁇ m.
• the height advantageously exceeds 70 ⁇ m and the edges of the bumps should have a slope angle of at least 20°.
• an advantageous embodiment of surface structure 6 comprises elevations having, at least in one direction, a width W not exceeding 1 mm, preferably not exceeding 300 ⁇ in.
• the height H of the edges of the eleva ⁇ tions should be as described in the preceding paragraph.
• Eleva.tions of this type can e.g. be formed by dye lines applied to substrate Ia by means of intaglio printing.
• the distance D (see Fig. 4) between neighboring non- intersecting edges formed by surface structure 6 should not exceed 1 cm.
• the surface structure is advantageously not formed by the edges of items applied to the substrate that are recognized as "separate" therefrom, such as a photograph.
• surface structure 6 has been created by adding material to the surface of substrate Ia, and it has also been mentioned that the surface structure can be generated by embossing. It is also possible to manufacture or change the surface struc ⁇ ture by flattening a rough or structured surface area of substrate Ia, e.g. by embossing parts of it with a flat stamp prior to the application of hologram layer 5.
• the surface of substrate Ia may be a rough paper with the exception of those places where it has been flattened with the stamp.
• hologram layer 5 was deformed non-homogeneousIy by surface struc ⁇ ture 6.
• hologram layer 5 can also be non-homogeneousIy deformed by apply ⁇ ing non-homogeneous pressure thereto, e.g. in an emboss ⁇ ing process .
• stamp 15 comprises a surface structure 16 consisting e.g. of recesses or bumps at its impact side 17. Pressing stamp 15 against hologram layer 5 on sub ⁇ strate Ia (or prior to attaching hologram layer 5 onto substrate Ia) creates a corresponding non-homogeneous de- formation 18 therein. This again leads to visually per ⁇ ceptible distortions 10 within volume hologram 7. To en ⁇ courage deformation, hologram layer 5 can again be heated prior to and/or during embossing.
• volume holo- gram 7 was, prior to deformation of hologram layer 5, ho ⁇ mogeneous.
• volume hologram 7 can also be non-homogenous and represent a desired two- or three-dimensional image.
• a visible structure in volume hologram 7 can either be written into the original hologram during manufacturing, or it can be caused by the inhomogeneous deformation of the hologram layer.
• a further security feature can be created. This is shown in Fig. 6, where the cross- hatched area 11 depicts a first pattern that was written into the original hologram and visible therein without further distortion, while the dotted area 12 depicts a further pattern generated in homogeneous areas of the hologram by means of a local deformation of hologram layer 5.
• deforming hologram layer 5 care is taken that the edges of first pattern 11 are collinear with the edges of second pattern 12. This allows the user to ver ⁇ ify that hologram layer 5 has been applied correctly.
• the areas 10 of inhomogeneous deformation in volume hologram 7 can have any desirable shape. Advanta- geously, they follow the contours of characters or geo ⁇ metric shapes that can be recognized easily.
• the inhomogeneous deformations applied to the volume hologram can also be caused by a plurality of lo ⁇ cal deformations having extensions of a e.g. 50 ⁇ m or less in the directions parallel to the surface of the substrate.
• a surface structure having random bumps or a cross hatching pattern can be used. Even though such structures are not individually recognizable, they distort the hologram in random manner.
• the re- flections from the hologram have decreased angular and spectral selectivity, which can be recognized by a viewer and increases the visibility of the hologram under dif ⁇ fuse illumination.
• the il ⁇ luminating light can be diffuse and does not need to be coherent.
• the property can e.g. be the visibility of colored reflections near the bumps of surface structure 6. In more general terms, the property will usually be any reflection (or absence of reflection) caused by the deformation of volume holo- gram 7.
• step 2 If the property checked in step 2 is not found, the authenticity of the object can be negated.

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• 2004
  • 2004-06-30 EP EP04738056.3A patent/EP1765600B2/en active Active
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